Max lift on a GenVI roller set up ?????

[doctor_ratz]

I am planning on using 500hp cams in a genVI block (crane p/n 169611) lift is .576 / .598. That is over the .570" reccomended lift for the stock roller lifters, but I was running a .640" lift with stock GM rollers and did not have a problem. Was I lucky, or can I get by at .598 lift and stock GM roller lifters.

[Raylar]

It really has a lot to do with the base circle size on the camshaft that you are getting. We use new billets and grind our bigger camshafts with lifts up to .630" on a camshaft that after grinding still has a 1.250" base circle size and we have no problems with stock GEN VI dogbones and lifters. If your camshaft has a base circle size of lets say 1.200" or smaller you will have problems. Most users don't realize how important base circle size is in this equation.
When valve lifts get above about .625" and above the base circle on the camshaft will get to be 1.200" or smaller and depending on what one ends up with for a base circle size, careful attention needs to be paid to lifter length to avoid serious problems that will come from the lifter dropping out of the dogbone and rotating (disasterous)! This is where long body roller lifters are needed in a Gen VI BBC.
Some camshaft grinders use smaller base circle size base billets and the resulting overall base circle size will get smaller depending on the lifts used.
Again, its all in the details and sometimes seemingly little things can make a huge difference.
Glad to see you are asking the question and paying attention to the DETAILS!

Best Regards,
Ray @ Raylar